Its hard to see but there is a wood block bolted to the aluminum frame of the dolley. This block slips nicely over the end of the trailer closest the back of the van. Its virtually impossible for the dolly/boat to slide backwards. Once I crank down the tiedowns with the ratchets. FAGGETABOUTIT. Now I have the trailer situation figured out I'm now have no excuses for not learning how to sail it. My wife keeps laughing that all I do is fool around with the trailer but she doesn't see any sailing going on.